[Samba] When is a machine SID created?

[Taso Hatzi]

I have been having a problem with 'net getdomainsid' on a machine that I
set up to be a BDC.

# net getdomainsid
Could not fetch local SID

tdbdump shows that there is no machine SID in secrets.db, so I'm thinking
that I overlooked the step that creates a machine SID. What creates the machine
SID and when? Also, is it the hostname or the netbios name that samba uses as
the machine name?

I intend to promote the BDC to PDC eventually, and for practical purposes, give
it the name of the former PDC. Do I have to explicitly do anything to update the
secrets.tdb file or does Samba detect name changes?

There is an LDAP backend all this which has entries for both the PDC
and the BDC.